Refrigerator employing secondary refrigeration system



Dec. 22, 1953 H, M. ULI- STRAND 2,653,159

' REFRIGERATOR EMPLOYING; SECONDARY'REFRIGERATION SYSTEM Filed April 26,v 195o IN VEN TOR.

BY@ KM Maul Patented Dec. 22, 1953 UNITED crrics REFRIGERATOR EMPLOYING SECONDARY REFRIGERATION SYSTEM Hugo Malcolm Ullstrand, Stockholm, Sweden, assignor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation of Sweden 13 Claims.

My invention relates to refrigeration, and more particularly concerns cooling of a thermally insulated interior of a refrigerator with the aid of a secondary refrigeration system.

It is an object of my invention to provide an improvement for cooling an interior of a refrigerator with the aid of a secondary refrigeration system whereby better vdistribution of cooling effect may be obtained.

Another objectof my invention is to provide an improvement for transmitting cooling eifect from a primary evaporator or cooling element to the interior of a refrigeratorv whereby a single secondary refrigeration system can be employed to transmit such cooling effect over a wide temperature range including temperatures above and below the freezing temperature of water.

A further object of my invention is to reproduce a temperature gradient in the secondary evaporator of a heat transfer system which is generally like the temperature gradient of a primary evaporator with which the heat transfer system is associated. l v

A still further object is to provide a secondary refrigeration system for transferring cooling effect over a wide temperature range from an evaporator or cooling element having a temperature gradient and forming a part of an absorption refrigeration system employing evaporation of refrigerant nuid in the presence of an inert gas or auxiliary agent.

The above and other objects and advantages of the invention will be better understood from the following descriptiony taken in connection with the accompanying drawing forming a part of this specification, and in which Fig. l is a view more or less diagrammatically illustrating an absorption refrigeration system of the inert gas type to which the invention has been applied; and Fig. 2 is a vertical sectional view of a refrigerator and cooling element therefor which embodies the invention and is associated with a refrigeration system like that shown in Fig. 1.

In Fig. 1 I have shown an absorption refrigera tion system of a uniform pressure type which is well known in the art and in which an inert pressure equalizing gas'is employed. Such a refriger vation system comprises a generator or boiler l@ containing a refrigerant, rsuch as ammonia, in solutionv in a body 'of absorption liquid, `such as water. Heat may be supplied to the Iboiler id from a heating tube or flue i l thermally connected therewith, as by welding. The heatingV tube Il may be heated in any suitable mannery as by a liquid or gaseous fuel burner l2, for example,

ofi'

2 which is adapted to project its flame into the lower end of the tube.

The heat supplied to the boiler Il? and its contents expels refrigerant vapor out of solution, and the vapor thus generated ows to an air-cooled condenser I4 in which it is condensed and liquefied. Liquid refrigerant flows from condenser I4 through a conduit l5 into a cooling element I6 in which it evaporates and diffuses into an inert pressure equalizing gas, such `as hydrogen, which` enters the lower part thereof from a gas heat exchanger il. Due to evaporation of refrigerant fluid into inert gas, a refrigerating effect is produced, as will be explained more fully hereinafter.

The rich gas mixture of refrigerant vapor and inert gas formed in cooling element l@ flows from the upper part thereof through a conduit I8, gas heat exchanger Il, conduit I9 and absorber vessel 2@ into the lower part of an absorber coil-2l. In absorber coil 2l the rich gas mixture flows countercurrent to downwardly flowing absorption liquid which enters through a conduit 22.

The absorption liquid absorbs refrigerant vapor from inert gas, and inert gas weak in refrigerant flows from the upper part of absorber coil 2i in a path of flow including the gas heat exchanger Il into the lower part of cooling element I5. Y

The circulation of gas in the gas circuit just described is due to the dierence in specific weight of the columns of gas rich and weak, respectively, in refrigerant vapor. Since the column of gas rich in refrigerant vapor and flowing from cooling element It to the absorber coil 2 IV is heavier than the column of gas weak in refrigerant vapor and flowing from absorber coil 2l to cooling element it, a force is produced or developed within the system for causing circulation of gas in the manner described.

Absorption solution flows downwardly through coil 2! into the absorber vessel 2d and such solution, which is enriched in refrigerant, passes from the vessel through a conduit 23 and an inner passage or pipe 24 of liquid heat exchanger 25 into the lower end of a vapor lift pipe or tube 2t which is in thermal exchange relation with the heating tube ll, as by welding. Liquid is raised by vapor-liquid lift action through pipe 26 into the upper part of boiler l0. Refrigerant vapor expelled out of solution in boiler lil, together with refrigerant vapor entering through pipe 25, flows upwardly from the boiler to the condenser l 4, as previously explained. Y

The outlet end fof condenser I4 is connected by an uppeextension of conduit l5 and a conduit 2li to a part of the gas circuit, as to the upper part of absorber coil 2l, for example, so that any inert gas which may pass through the condenser it can new into the gas circuit. The absorption liquid from which refrigerant vapor has been expelled news from the boiler lil through a connection 28, an outer pipe or passage 29 of the liquid heat exchanger and conduit 22 into the upper part of the absorber coil 2i. The circulation of absorption solution in the liquid circuit just described is eiected by raising of liquid through ipe gli.

In order to simplify Fig. 1, the cooling element I6 has been illustrated apart from a household refrigerator. It has already been proposed to employ cooling elements of absorption refrigeration systems like that just described to transmit cooling effect to the interior of a refrigerator cabinet with the aid of a secondary refrigeration system. In such known arrangements it had usually been the practice to transmit cooling eifect to the interior of the cabinet from a cooling element or evaporator section of a primary refrigeration system which operates at a temperature above the freezing temperature of water, so that food preservation may be eilected without dehydration.

In accord with my invention cooling effect is transmitted from cooling element it to the in- -terior of a household refrigerator Se in such a manner that a single secondary refrigeration system can be advantageously employed to transmit cooling effect throughout a wide temperature range below and above the freezing temperature of water. As shown in Fig. 2, the household refrigerator 33 comprises a cabinet 3i having inner metal shells 32 and 33 arranged to be supported within an outer metal shell 34 and insulated with any suitable insulating material 35.

The inner metal shells 32 and 33 define thermally insulated storage compartments 36 and 3l, respectively, which are located one above the other and separated by a horizontal insulated partition 38. Access may be had to the compartments i and 3l through a door 39 which is hinged to the front of the cabinet 3l, a gasket l0 being provided on the door to form an airtight seal when the door is closed and the gasket contacts the front marginal portions 4i and 42 of the cabinet 3l and horizontal partition 38, respectively.

The secondary refrigeration system of the invention, which also may be referred to as a seoondary heat transfer system, comprises a condenser or condensation portion 43 in the form of a looped coil, an evaporation portion which includes a looped coil 44 and vessel e5, and connections between these parts which will be described presently. The cooling element i t of the absorption refrigeration system described above, which may be referred to as the primary cooling element, is arranged in good heat conductive relation with the condensation portion 43 of the secondary refrigeration system. This may be accomplished in any suitable manner, and, by way of example, the cooling element I3 and condensation portion 42 are embedded in metai castings 46 and M, respectively, which can be maintained in good thermal contact with one another by suitable resilient means, not shown.

As described above, liquid refrigerant is ccnducted to primary cooling element i6 for downward gravity flow therethrough. Inert gas ilows upwardly through the cooling element i6 in counterow to liquid refrigerant. The refrig- 4 erant fluid evaporates and diiuses into the inert gas to produce a cooling or reirigerating eiect which is transmitted to the condensation portion i3 of the secondary refrigeration system.

Since the inert gas ilows upwardly through the vertically extending cooling element i5, the gas in the lower part thereof contains a lesser amount of refrigerant vapor than the gas in the upper part thereof. rThe partial vapor pressure of the refrigerant is a gradient, so that the temperature of liquid refrigerant in the cooling element is also a gradient, the evaporating temperature of liquid being lower in the bottom part of the cooling element I6 and increasing in the upward direction of flow of the inert gas.

In order to utilize the temperature gradient of the primary cooling element most advantageously for transmitting cooling ei'ieet to the interior of refrigerator Si), the secondary refrigeration system is charged not only with a suitable volatile refrigerant or heat transfer fluid but also with a relatively dense or heavy noncondensible or inert gas, so that the refrigerant vapor pressure and temperature corresponding thereto will vary throughout the secondary evaporation portion from the extrei 1e upper part oi coil d4 to the vessel i5 which communicates with the lower end of such coil.

In a manner which will be described presently, the volatile heat transfer iiuid evaporates within coil 44 and vessel l and taires up heat thereby transmitting cooling effect and cooling the compartments 36 and 3l. The vapor ilo-ws upwardly through coil lli and conduit le into the upper part of the secondary condenser and the vapor is cooled and condensed by the primary cooling element it. From the secondary condenser condensate ilows through a connection 49 into a U-shaped liquid trap Eil. Tihe condensate passes from liquid trap Eid into the evaporation portion of the secondary refrigeration system, and in so doing passes downwardly by gravity flow through coil il-l and collects in vessel d5.

The dense non-condensible or inert gas contained in the secondary refrigeration systen passes from the connection ed through a conduit 5| whose lower end isA connected to vessel A suitable dense or inert gas is employed which is appreciably heavier than the vapor the heat transfer iluid, so that such dense gas will naturally pass downwardly in conduit 5i; By way or" example, ammonia for ethyl chloride be selected as the secondary refrigerant or volatile heat transfer fluid and sulfur hexai'luoride (SFC.) may be selected as the dense and heavy inert gas.

It will now be understood that the secondary refrigerant passes downwardly through coil. into vessel d5 while the dense inert gas is introduced into the evaporation portion or" the secondary system at the vessel t5 and passes upwardly through coil The secondary reir-igerant or volatile uid evaporates and diffuses into the dense gas and takes up heat thereby abstracting heat from the surroundings. Hence, the dense inert gas in the lower part or" the secondary evaporator or evaporation portion'contains a lesser amount of vapor or the volatile heat transfer fluid than the inert gas in the upper part thereof. Accordingly, the partial vapor pressure of the volatile heat transfer fluid will be a gradient, so that the temperature of volatile heat transfer fluid in the coil will also be a gradient, the evaporating temperature of the volatile fluid being lower in lthe vessel 'i5 and bottom part of coil Il@ and increasing in the upward direction of oW of the dense inert gas inthe coil 44.

ln View of the foregoing, it will now be seen that the secondary refrigeration system of the invention will be capable of transmitting cooling eect throughout the temperature range of the primary cooling element I6, and the temperature stratification in the secondary evaporator formed by the coil dll and vessel `liti Will correspond to the temperature gradient in the primary cooling element i5.

Since the primary cooling element is capable of operating at temperatures below the freezing temperature of Water in the lower part thereof and operating at above freezing temperatures in the upper part thereof, the interior of refrigerator 38 can be divided to take advantage vof the sub-freezing temperatures produced in the vessel e5 lower part of coil 44. Y Hence, the bottom compartment 3l may be employed as the low temperature storage space and may be operated at a sufiiciently low temperature to store frozen food packages and produce ice cubes in trays containing Water adapted to be frozen.

The upper part of coil dll which may be operated at a temperature above the freezing temperature of water may be advantageously ernpl-oyed to effect cooling of the upper storage compartment 38. partment -Bi will be maintained at a higher temperature than the lower Icompartment 3i and hence will be maintained at a higher hureiditv. While in Fig. 2 the coil dll has been diagrammatically illustrated as being disposed within the compartments and 3l, it will be understood that in practice the coil d4 may be arranged to abstract heat from the interior of the refrigerator 3d in any suitable manner. For example, the coil dd be embedded in the insulation and arranged in good thermal Vcontact with the outer surfaces of the inner liners 32 andk 33 define ing the storage compartments Sii and 3l. The vessel l5 form the bottom supporting surface of the lower compartment 3l or may be arranged in goed thermal contact with the underside of the inner liner defining such lov'er compartment. The inert gas conduit '5| also is desirably embedded in the insulation 35 and out of direct contact with the inner liners 32 and 33. It will be observed that a rear apparatus `compartment 52 is provided in cabinet 3i for housing the primary refrigeration system of Fig. l.

Ann important consideration in practicing the invention the proper selection of an inert gas which is dense and relatively heavy compared to the vapor of the volatile heat transfer fluid. This is so because it is desirable to produce a driving force of highl magnitude Within vthe secondary refrigeration system to cause circulation of the inert In the connection e9 the partial vapor pressure of the volatile fluid or sec.- ondary refrigerant is relatively low following condensation of such fluid in the secondary coni denser fili. Accordingly, the gas passing into the upper end of conduit 5l is of high density and considerably heavier than the gas .mixture of inert gas and secondary refrigerant vapor in coil .fl-fl. Due to the difference in specific Weight of the columns of heavy gas in conduit 5l and the lighterrgas mixture in coil lili, a driving force is produced Within the secondary refrigerating system for causing circulation of gas in the manner described. This driving force can be intensified In any event, the storage corn-l 6 by employing tubing for conduit 5l and coil M which is of reduced size.

While a single embodiment of the invention has been shown and described, it Will be appar-I ent to those skilled in the art that various modifications and changes may be made Without departing from the spirit and scope of the invention, as pointed out in the following claims.

What is claimed is:

1. A refrigerator including a cabinet having first and second thermally insulated compartments, a primary evaporator having portions operable at average or mean temperatures above and below the freezing temperature of water, a closed heat transfer system containing refrigerant fluid and a non-icondensible gas whose specifio Weight is greater than that of the refrigerant fluid in vapor phase, said system comprising a condensation section in heat exchange relation with both portions of said primary evaporator and a vaporization section including one portion in thermal relation with said first compartment and another portion in thermal relation With said second compartment, and means Vcomprising said closed heat transfer system for transferring cooling effect from both portions of said primary evaporator to said compartments to maintain one of said compartments at an average or mean temperature below the freezingI temperature of water and the other of said compartments at an average or mean temperature above the freezing temperature of Water.

A refrigerator including a cabinet having several thermally insulated compartments, a primary cooling unit having first and second por-` tions operable at different average temperatures, a closed heat transfer system containing refrigerant fluid and a non-condensible gas whose specific Weight is greater than that of refrigerant fluid in vapor phase, said system comprising a condensation section in heat exchange relation with both the first and second portions of said primary cooling unit and a vaporization section having one portion in thermal relation with one of said compartments and another portion in thermal relation with another of said compartments, and means comprising said closed heat transfer system for transferring cooling effect from both the rst and second portions of said primary cooling unit to said compartments to maintain one of said compartments at a low average temperature and another of said compartments at a higher average temperature.

In a method of transferring cooling effect in which refrigerant fluid is vaporized in a place of vaporization and such vaporized refrigerant is condensed in a place of condensation in heat exchange relation with a source of refrigeration having a gradient temperature and the condensate is returned to the place of vaporization, the improvement which comprises circulating a noncondensible gas through and between said places vof vaporization and condensation in a closed cir- .relation with successively lower temperature portions oi the source of refrigeration, and in another portion of which non-condensible Weak in vaporized refrigerant flows from the place of condensation to another region of the place of Vaporization for ilovv therethrough to said one region. 4. In a method of transfer ing cooling effect in which refrigerant fluid is vaporized in a place of vaporization and such vaporized fluid is condensed in a place ci condensation in heat exfchange relation with a primary source of refrig eration and the condensate is returned to the place of vapor-ization, the improvement which comprises nowing condensate formed in the place of condensation to a place or accumulation, overiowng liquid at a place to which condensate flows from a region below the liquid surface level at the place or accumulation, conducting such overflow liquid to the place or vaporization for gravity new through the latter, circulating a noncondensible gas through and between said place of Vaporicaticn and condensation in a closed circuit in one portion o1 which the non-condensible gas hows upwardly in a vertically extending path of flow in the place of vaporication in the presence ci downwardly ilowing condensate and in another portion. oi which non-condensible gas weak. in rei; gerant flows from the vapor space above the liquid surface level in the place oi accumulation to the lower end of the vertically extending path of not: in the place of vaporization.

5. In a method oit "ransierring cooling eect in which liquid refrige ant is vapcrlaed in a place of vaporization and such vaporized refrigerant is condensed in a place or condensation in heat exchange relation with a primar.; source of refrigeration and the liquid condensate is returned to the place or vaporization, the improvement which comprises circulating between said places of vaporization and condensation and in one direction through each of said places above the lifuid surfaces therein a non-condensible gas Whose specific weight is greater than that of the refrigerant iiuid in vapor phase.

(i. The method of transferring cooling eiTect which comprises flowing a non-condensible gas to one end or a vertically extending path of ow in a place of vaporication, introducing liquid refrigerant to a region of the place or" vaporization for new therethrough Without blocking now of non-condensihle gas in said path oi'ow, vaporizing liquid reirigerant in the place of vaporization in the presence of the non-condensible gas, flowing a mixture of refrigerant vapor and noncondensiole gas from the opposite end of said vern tically extending path of now in the place oi vaporization to a place of condensation in heat exchange relation with a source of refrigeration so as to ligue-ly the refrigerant out of the gas mixture, returning non-condensilole gas from the place ci am. @sation to said one end of the vertically extci ng path of flow in the place of vaporiaa and dov/ing liquid refrigerant from the place of condensation to said region at which such liquid is introduced to the place of vaporization for non' therethrough.

7. ln combination with a primary source of re irigeration, a secondary cooling system comprising a condenser in heat exchange relation with the primary source of refrigeration and an evaporater, said cooling system being hermetically closed and containing refrigerant fluid and a noncondensilole gas whose density is appreciably greater than the refrigerant duid in vapor phase, said evaporator comprising structure providing an elongated path or now for uids, conduit means for conducting liquid refrigerant formed in said condenser to the upper part of said evaporator for gravity flow through the latter, conduit means for conducting non-oondensible gas enriched in reirigerant vapor iroxn the upper part of said evaporator to said condenser, and conduit 8 means for. separating non-condensible gas Weak in refrigerant vapor from liquid formed in said condenser and conducting such separated gas to the lower part of said evaporator for upward flow through the elongated path of ow in the latter.

8. In combination with a primary source of refrigeration, a secondary cooling system comprising a condenser in heat exchange relation with the primary source of refrigeration and an evaporator, said cooling system being hermetically closed and containing refrigerant fluid and a noncondensihle gas whose density is appreciably greater than the refrigerant ud in vapor phase, said evaporator comprising structure providing an elongated path of flow for fluids, a connection including a liquid trap for conducting liquid refrigerant formed in said condenser to the upper part of said evaporator for gravity flow in the latter, conduit means for conducting non-condensble gas enriched in refrigerant vapor from the upper part of said evaporator to said condenser, and means including said liquid trap for separating non-condensible gas weak in refrigerant vapor from liquid formed in said condenser and conducting such separated gas to the lower part of said evaporator for upward ilovv through the elongated path of flow in the latter.

9. In combination with a primary source of refrigeration, a secondary cooling system com'A prising a condenser in heat exchange relation with the primary source of refrigeration and an evaporator, said cooling system containing refrigerant iluid and a non-condensible gas, said evaporator comprising structure providing a vertically extending elongated path of ilow for fluids, conduit means for conducting liquid refrigerant formed in said condenser to the upper part of said evaporator for gravity now through the latter, conduit means for conducting non-condensihle gas enriched in refrigerant vapor from one end of said evaporator to said condenser, and means for separating non-condensible gas weak in refrigerant vapor from liquid formed in said condenser and conducting such separated gas to the opposite end of said evaporator for flow through the elongated path of flow in the latter, said cooling system being hermetically closed to provide circuits for refrigerant fluid and the noncondensible gas in which circulation of the gas is effected solely due to the varying partial pressure of refrigerant vapor in different parts of the circuit for non-condensible gas.

lil. ln a reirigerator having a cabinet divided into several compartments at diierent levels, prin mary absorption refrigeration apparatus including an evaporator in which refrigerant evaporates in the presence of an inert gas circulating therethrough, such evaporator having a temperature gradient in which successive portions in the direction of gas flow operate at increasingly higher temperature levels, an hermetically closed secondary cooling system comprising a condenser in heat exchange relation with said evaporator and a vertically extending cooling element having a lower portion arranged to abstract heat from one compartment and a higher portion arranged to abstract heat from another compartment at a higher level, said secondary system containing refrigerant fluid and a non-condensible gas Whose specic Weight is greater than that of the refrigerant fluid in vapor phase, a connection for conducting liquid refrigerant formed in said condenser to said cooling element for gravity flow therethrough in the presence ofthe non-condensible gas, a connection for conducting a mixture of non-condensible gas and vaporized refrigerant y from the higher portion of said cooling element to said condenser and another connection for separating non-condensible gas from liquid formed in said condenser and conducting such separated gas to the lower portion of said cooling element, said condenser being formed and arranged to provide a path of flow for the gas mixture formed in said cooling element in which the gas mixture in the direction of flow comes in heat exchange relation with successively cooler portions of said evaporator.

11. In a refrigerator having a cabinet divided into several compartments at diierent levels, primary absorption refrigeration apparatus including an evaporator, an hermetically` closed secondary cooling system comprising a condenser in heat exchange relation with said evaporator and a vertically extending cooling element having a lower portion arranged to abstract heat from one compartment and a higher portion arranged to abstract heat from another compartment at a higher level, said secondary system containing refrigerant fluid and a non-condensible gas whose specic weight is greater than that of the refrigerant fluid in vapor phase, a connection for conducting liquid refrigerant formed in said condenser to said cooling element for gravity flow therein in the presence of the non-condensible gas, a'connection for conducting a mixture of non-condensible gas and vaporized refrigerant from the higher portion of said cooling element to said condenser, and another connection for separating non-condensible gas from liquid formed in said condenser and conducting such separated gas to the lower portion of said cooling element.

12. In a refrigerator having a cabinet divided into several compartments at different levels, primary absorption refrigeration apparatus including an evaporator, a secondary cooling system comprising a condenser in heat exchange relation with said evaporator and a vertically extending cooling element having a lower portion arranged to abstract heat from one compartment and a higher portion arranged to abstract heat from another compartment at a higher level, saidy secondary system containing refrigerant fluid and a non-condensible gas, a connection for conducting liquid refrigerant formed in said condenser to said cooling element for gravity flow therein in the presence of the non-condensible gas, a connection for conducting a mixture of noncondensible gas and vaporized refrigerant from one end of said cooling element to said condenser and another connection for separating noncondensible gas from liquid formed in said condenser and conducting such separated gas to the other opposite end of said cooling element, said cooling system being hermetically closed to provide circuits for refrigerant uid and the noncondensible gas in which circulation of the gas is effected solely due to the varying partial pressure of the refrigerant vapor in different parts of the circuit for non-condensible gas.

13. In a method of transferring cooling effect in which liquid refrigerant is vaporized in a place of vaporization and such vaporized refrigerant is condensed in a place of condensation in heat exchange relation with a source of refrigeration and the liquid condensate is returned to the place of vaporization, the improvement which comprises circulating a non-condensible gas in a closed circuit between said places of vaporization and condensation and in one direction through each of said places.

HUGO MALCOLM ULLSTRAND.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,923,472 Baird Aug. 22, 1933 1,926,384 Hull Sept. 12, 1933 2,033,554 Smith Mar. 10, 1936 2,044,609 Hedlund June 16, 1936 l 2,142,828 Smith Jan. 3, 1939 2,261,681 Ullstrand Nov. 4, 1941 2,261,682 I-IedlundV Nov. 4, 1941 2,261,683l Kuenzli Nov. 4, 1941 2,268,381 y Brace Dec. 30, 1941 

